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Monday, November 7, 2016

Alternate Day Fasting: Does it Matter How You Time (Lunch / Dinner) & Distribute (1 or 3 Meals) Your Fasting Day Meals?

This & other studies show no increased binge eating risk on non-fasting days.

Yes, yes, ... I hear ya. Meal- and nutrient timing has been ridiculously overrated in the health and fitness community for years. To ignore a potential effect of when you eat completely, however, is about as stupid as the notion that your training was wasted if you don't get a 30-50g bolus of protein within the first 30 minutes of racking the weights.

In view of the far-reaching effects of our biological clock and its close interaction with food intake and nutrient availability, it is, after all, only logical to assume that food timing could have a significant effect on our metabolic health.

Previous research suggests that at least some of the benefits of intermittent or alternate day fasting are mediated by the interaction of the fasting / feeding cycle with our circadian rhythm. If that's indeed the case (and the evidence is quite convincing), it is not illusionary to assume that the timing of the meal(s) / feeding window on (intermittent) fasting days could affect the proven beneficial effects of these diet regimen, as well... I guess this or something like this was also what Kristin Hoddy told her thesis adviser, Krista A. Varady, before she started her research into the effects of "Meal Timing during Alternate Day Fasting". Research, the results of which have just been published by the University of Illinois at Chicago (Hoddy. 2016).

The trial itself consisted of a two-week lead-in followed by 8 weeks of alternate day fasting (ADF) - a basic template that identical for all subjects (BMI between 30 and 39.9 kg/m²; age between 25 and 65 years), the time at which the subjects were told to consume their only meal on the fasting day, however, differed for the three study groups the N = 74 subjects were randomly (stratified based on sex, age, and BMI) assigned to:

in the ADF-L group, the subjects consumed their only meal at launch

in the ADF-D group, the subjects consumed their only meal at dinner, and

in the ADF-SM group, the ~500kcal were split into small meals throughout the day

All subjects consumed 25% of their baseline energy needs on a fast day (24 h), and ate ad libitum on each alternating feed day (24 h). The feed and fast days began at midnight each day. Subjects were asked to refrain from staying up until midnight on feed days, or getting up just after midnight following a fast day, to eat. Subjects were provided with meals on each fast day, and ate ad libitum at home on the feed day.

Table 1: The meals for the fast days were prepared for the subjects; here's the nutrient composition (Hoddy. 2016).

All ADF fast day meals were prepared in the metabolic kitchen of the Human Nutrition Research Center (HNRU) at the University of Illinois, Chicago (they were provided as a 3-day rotating menu, see Table 1). With the exception of energy-free beverages, tea, coffee, and sugar-free gum, no other 'foods' were allowed on the fasting day. On which the meals were consumed timed accordingly to the previously outlined scheme: ADF-L between 12.00 pm and 2.00 pm; ADF-D between 6.00 pm and 8.00 pm and ADF-SM group divided their fast day meal up into 3 mini meals that were consumed between 6.00 am and 8.00 am (~100kcal), between 12.00 pm and 2.00 pm (~300kcal), and between 6.00 pm and 8.00 pm (~100kcal).

Figure 1: Changes in body weight and body composition during the weight loss period (Hoddy. 2016).

And as you can see in Figure 1, the effect of timing differed for the changes in body composition, which were identical in all three groups, and the reduction in visceral body fat that was greater, albeit not statistically significantly greater in the ADF-D and ADF-SM groups.

Intermittent fasting (ADF or lean-gains style) spares muscle as you're dieting: I have discussed the results of the first head-to-head comparison of a true alternate day fast vs. regular caloric restriction, only recently (read the article), but the respective study is not the only paper that discusses the efficacy of alternate day fasting and regular calorie restrictions. A recent systematic review and meta-analysis by Alhamdan et al. concludes (in line with what I've written in the previously referenced article] "that ADF is an efficacious dietary method, and may be superior to VLCD [very low-calorie diet] for some patients because of ease of compliance, greater fat mass loss and relative preservation of fat-free mass" (Alhamdan. 2016).

With visceral fat being one of the drivers of inflammation and the metabolic syndrome, it would thus seem as if eating only one meal and eating this meal between 12 pm and 2 pm was a bad idea if your goal was to improve your metabolic health. Other parameters Hoddy analyzed do yet not support this notion. In fact, not a single of the metabolic disease factors she tracked during the 10-week study showed significant inter-group differences.

Figure 2: Changes in metabolic disease factors over the course of the study (Hoddy. 2016).

If you scrutinize the data in Figure 2, you may argue that there are trends which appear to favor having only one meal and having it at dinner. And you're right. If we discard the statistical non-significance of the differences, the ADF-D regimen clearly had the most beneficial, while the ADF-L regimen had the smallest effects on glucose management. The differences, however, are far from reaching statistical significance (p = 0.87, p = 0.66, p = 0.68 for fasting blood glucose, insulin, and HOMA-IR, respectively) and the effects on blood lipids are devoid of any inter-group differences that are worth mentioning (statistically significant or not).

"Improvements in LDL particle size occurred in all of the groups. This was marked by an increase in the
proportion of large LDL particles in all intervention groups, and a decrease in the proportion of small
LDL particles in only the ADF-D and ADF-SM groups. This shift in LDL particle size represents a
reduction of atherosclerotic risk."(Hoddy. 2016)

Overall, it does therefore probably not matter when you consume your ADF 'fast day meal', what will matter, however, is that you are able to stick to the rules, i.e. to not consume any other foods and based on my own intermittent fasting experience, that's going to be increasingly hard with both, the ADF-L and the ADF-SM regimen - corresponding data is unfortunately not available, because Hoddy et al. analyzed parameters such as the change in appetite hormones after weight loss only based on pooled ADF data.

True Alternate Day Fast Beats Classic Dieting: Max. Fat, Min. Muscle Loss, No 'Metabolic Damage' in 32 Wk Human Study - If you haven't read this recent SuppVersity article, yet, I highly suggest you do it now. It provides the first evidence from an RCT that indicates that intermittent fasting / ADF allows for easier and more efficient fat (not just weight) loss | read it

So, once again: Meal timing doesn't matter? Well, the three meal pattern appears to have the smallest effect on the subjects RMR and the all-calories-for-dinner pattern clearly had the most beneficial effects on glycemia... but the difference - and that's the case for all parameters the scientists measured - was statistically non-significant.

Eventually, it would thus seem as if it all came back to the tried and proven principle according to which "the best diet is always the diet you can adhere to" and adherence is actually a huge strength of intermittent fasting diets (Varady. 2011; Klempel. 2013); most people find it much easier to achieve a decent caloric deficit with these diets compared to the classic calorie restriction... no wonder, a recent study (Catenacci, et al. | discussed here) showed better results with ADF vs. classic calorie restriction | Comment!

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